Conventionally, various tactile presentation devices have been contrived which provide a tactile sense, such as vibration, to the finger of an operator according to an operation input when the finger of the operator directly touches an operation input unit, such as a touch panel or a button. For instance, Patent Literature 1 describes a portable electronic device as a tactile presentation device. The tactile presentation device has a basic structure as shown in FIG. 14. FIG. 14 is a cross-sectional view showing the structure of a conventional tactile presentation device 10P. FIG. 14 shows the cross section of the tactile presentation device 10P in a plane parallel to the side surface thereof.
The tactile presentation device 10P has a chassis 100P including a top surface chassis 101P and a bottom surface chassis 102P. The top surface chassis 101P has a top surface on the operation surface side, a side surface orthogonal to the top surface, and a top surface inner space 110P. The bottom surface chassis 102P has a bottom surface opposite to the top surface of the top surface chassis 101P, a side surface orthogonal to the bottom surface, and a bottom surface inner space 120P. The side surfaces of the top surface chassis 101P and the bottom surface chassis 102P are joined to each other. The top surface inner space 110P and the bottom surface inner space 120P thus communicate with each other. With this structure, the chassis 100P has an inner space having a predetermined area.
Openings 111P are formed in the top surface of the top surface chassis 101P. An operation input unit 30P is arranged in the top surface inner space 110P of the top surface chassis 101P. The operation input unit 30P is a touch panel. The operation input unit 30P has an operation input surface exposed from the openings 111P to outside. The operation input unit 30P is mounted over the top surface chassis 101P via buffer materials 50P.
A holding member 121P is formed in the bottom surface inner space 120P of the bottom surface chassis 102P. The holding member 121P is projected from the bottom surface. A planar actuator 20P is held by the holding member 121P. The actuator 20P has a planar base substrate, and a planar piezoelectric element. Driving electrodes are formed on the piezoelectric element. The actuator 20P is held so that the planar surface of the base substrate is parallel to the operation input surface of the operation input unit 30P. The actuator 20P is held at the ends of the base substrate so that the base substrate is opposite to the operation input unit 30P and that the piezoelectric element is opposite to the bottom surface of the bottom surface chassis 102P.
A pad 40P is arranged between the surface of the actuator 20P on the operation input unit 30P side and the surface of the operation input unit 30P on the actuator 20P side. Height D of the pad 40P is previously set at the time of designing to coincide with the interval between the operation input unit 30P and the actuator 20P.
When the actuator 20P is driven, vibration is caused in the direction orthogonal to the planar surface of the base substrate. The vibration is transmitted via the pad 40P to the operation input unit 30P. The vibration transmitted to the operation input unit 30P is transmitted to an operator from his/her finger which touches the operation input unit 30P. With this, a predetermined tactile sense is presented to the operator.
PTL1: Japanese Patent Application Laid-Open (JP-A) No. 2010-152889
However, in the conventional tactile presentation device 10P as shown in FIG. 14, the following problems arise. FIGS. 15A and 15B are cross-sectional views of assistance in explaining the problems in the structure of the conventional tactile presentation device 10P. In FIG. 15A, the base substrate of the actuator 20P is thinner than the predetermined thickness. In FIG. 15B, the base substrate of the actuator 20P is thicker than the predetermined thickness. As in FIG. 14, each of FIGS. 15A and 15B shows the cross section of the tactile presentation device 10P in a plane parallel to the side surface thereof.
As shown in FIG. 15A, when the base substrate of the actuator 20P is thinner than the predetermined thickness, interval D′ between the actuator 20P and the operation input unit 30P is more than height D of the pad 40P (D′>D). Consequently, for instance, when the operation input unit 30P and the pad 40P are bonded to each other, as shown in FIG. 15A, gap Gap is caused between the pad 40P and the actuator 20P. With this, even when the actuator 20P is driven to cause vibration, the pad 40P is not contacted with the base substrate of the actuator 20P. The vibration cannot be transmitted to the operation input unit 30P.
As shown in FIG. 15B, when the base substrate of the actuator 20P is thicker than the predetermined thickness, interval D″ between the actuator 20P and the operation input unit 30P is less than height D of the pad 40P (D″<D). Consequently, as shown in FIG. 15B, load Strs is applied to warp the actuator 20P. The actuator 20P can be broken according to the magnitude of load Strs.
The above problems also arise when the height of the side surfaces of the top surface chassis 101P and the bottom surface chassis 102P is different from the desired height, when height D of the pad 40P is different from the desired height, and when the height of the holding member 121P of the bottom surface chassis 102P is different from the desired height. In the conventional structure, when the manufacture dimension accuracy of the components structuring the tactile presentation device, in particular, the manufacture dimension accuracy of the chassis 100P and the actuator 20P, is not high, vibration caused in the actuator 20P cannot be reliably transmitted to the operation input unit 30P and the actuator 20P can be broken.